We have shown earlier by two methods that the core protein of bovine sub-maxillary glycoprotein (BSM) contains over 80% of repetitive amino acid sequences of a glycopeptide containing 28 amino acids or its trimer; hundreds of these sequences make up the structure of the original BSM, which has the same amino acid composition as the small glycopeptides. The corresponding product from sheep (OSM) was found to have similar repeating sequences, but this aspect has not been clearly established. Since such "repeating units" are almost unique in proteins generally, we wish to test for their presence in other mucus glyco- proteins ("mucins" and "blood-group substances"). However, these repeating glycopeptides seem to be a mixture, with different amino acids in specific locations in the 28 amino acid sequence. We propose to separate and sequence the BSM glycopeptides with particular emphasis on the trypsin products. The causes of the microheterogeneity will be studied by preparing BSM from individual glands including pairs of glands from the same animals. A study will be made of the errors to be expected in the principal types of analyses used, in order to determine whether the differences in composition are greater than the experimental error. BSM injected in rabbits produces active antisera. We intend to show the effect of removal of carbohydrates, especially sialic acid, on the antigenic properties. The glycopeptide repeating units and the core protein will be used to establish the effect of molecular weight and removal of carbohydrates. We also intend to study the changes produced in the composition of hamster submaxillary and colonic cells resulting from exposure to chemical carcinogens.